Yesterday I ran after taking a day off. And decided that maybe the key to a sustained low heart rate workout is ... rest and a day off. Yesterday I ran and had another good workout. The max HR was 149. Perfect-- close to the wondrous Friday workout ("Freaky Friday"), but not too low. Freaky Friday was after two days off. Yesterday was after one day off. This is a picture compared to the Freaky Friday workout (note -- I wore my strap upside down for the first 20 or so minutes and got inconsistent data, but the point remains....) (Yesterday in lavender, Freaky Friday in blue):
Very close workout.
Now compare yesterday's workout with one two days earlier (the second day in a row of workin out (again yesterday in lavender and two days earlier in blue):
So maybe it is as simple as rest and recovery. I plan on running today so we'll see what happens on the HRM today.